In a metallic material, the flow of electric current will cause the movement of atoms. This effect is called the electromigration effect. The electromigration effect causes defects and has been a persistent trouble in the electronic industry. Thus, a number of techniques exist in overcoming the electromigration defects, e.g. using a coating to suppress the formation of hillock (Ho, et al, U.S. Pat. No. 4,680,854, 1987), using a coating to reduce the electromigration effect (Hu et al, U.S. Pat. No. 6,342,733, 2002), adding a small amount of copper into aluminum to form precipitates at the grain boundaries (Ames, et al, IBM J. Res. Develop., pp. 461-463, 1970; Kwok, Materials Chemistry and Physics, Vol. 33, pp. 176-188, 1993), or using a reaction to form precipitates at the grain boundaries (Howard, et al, U.S. Pat. No. 4,154,874, 1977). However, under the trend of miniaturization of conduction wire, all of the abovementioned methods cannot achieve a very good result. At present, the way the electronic industry solves this problem is using the copper wire to replace the aluminum wire in order to reduce the defects caused by the electromigration (Hummel, International Materials Review, Vol. 39(3), pp. 97-111, 1994). Even though copper has a better electric conductivity than aluminum and a weaker electromigration effect, the copper still has electromigration effect. It is expected that when the dimension of the wire is further reduced or the electric current density is further increased, the problems caused by the electromigration effect will emerge again. Therefore, it is necessary to develop another material that has no electromigration effect or an insignificant electromigration effect.
The electromigration effect caused by electric currents result in some atoms moving towards the cathode and yet moving towards the anode for some metals (Huntington, “Electromigration in Metals”, in “Diffusion in Solids: Recent Developments, pp. 303-353, edited by Nowick and Burton, Academic Press, New York, 1975). That means the effective charge numbers resulting from the electromigration effect can be a positive value or a negative value. When the effective charge number is a negative value, the direction of atom movement is identical to the direction of electron movement; on the other hand, when the effective charge number is a positive value, the direction of atom movement is opposite to that of the direction of electron movement. At present, there is no concept or technology of using metals of different positive/negative effective charge number to produce an alloy free of the electromigration effect.